1. Field of the Invention
The present invention relates to a stereolithography apparatus and, more specifically, relates to a stereolithography apparatus capable of improving the lamination precision and forming a highly precise three-dimensional model when stereolithography is performed by a constrained surface method.
2. Description of the Related Art
In the related art, stereolithography methods include a free surface method in which photocurable resin is irradiated with light from above and the resin is cured at the liquid surface, and a constrained surface method in which photocurable resin in a transparent container is irradiated with light from the bottom and the resin is cured at the bottom surface of the container (for example, refer to Japanese Unexamined Patent Application Publication No. 2001-328175).
As shown in FIG. 1, with a stereolithography apparatus configured to carry out fabrication by the free surface method, the fluid surface of photocurable resin 12 in a container 11 is exposed to the atmosphere. Here, the fluid surface of the photocurable resin refers to the interface of the photocurable resin to be irradiated with light.
With such a stereolithography apparatus, a stage 13, which is a platform for a three-dimensional model 14 to be fabricated, is lowered by a distance equal to the thickness of one cured layer from the fluid surface of the photocurable resin 12 so as to focus a fabrication laser beam at the interface of the atmosphere and the photocurable resin 12. In this way, a cured layer is formed at the fluid surface of the photocurable resin 12. By repeating this process, a plurality of cured layers is stacked to form the three-dimensional model 14.
However, with the free surface method, since the fluid surface of the photocurable resin 12 is exposed to the atmosphere, the surface precision of the cured layer is determined by surface tension and other factors. Thus, there is a limit to the lamination precision of the cured layers. Therefore, it is difficult to fabricate the three-dimensional model 14 with high precision.
As shown in FIG. 2, with the stereolithography apparatus configured to carry out fabrication by the constrained surface method, the fluid surface of the photocurable resin 12 contained in a container 21 is not exposed to the atmosphere and is constrained by a glass plate 23, which is provided at the bottom surface of the container 21. With this stereolithography apparatus, a stage 22, which is a platform for the three-dimensional model 14 to be fabricated, is lifted by a distance equal to the thickness of one cured layer from the fluid surface of the photocurable resin 12 so as to focus a fabrication laser beam at the interface of the glass plate 23 and the photocurable resin 12. In this way, a cured layer is formed at the fluid surface of the photocurable resin 12. By repeating this process, a plurality of cured layers is stacked to form the three-dimensional model 14.
As described above, with the constrained surface method, since the fluid surface is constrained by the glass plate 23, the surface precision of the cured layer is determined by the surface precision of the glass plate 23. Therefore, compared with the free surface method, the smoothness of the fluid surface can be improved, and thus, the lamination precision is improved. As a result, stereolithography can be carried out with high precision.